The ras oncogene undergoes point mutation in various tumor tissues in humans and is detected as an activated form capable of transforming normal cells. It is essential for the exhibition of transforming activity by the ras oncogene product that the 12th, 13th, or 61st amino acid should undergo mutation and also the cysteine residue at the C terminal region should be farnesylated for the membrane association of the ras oncogene product. This reaction is catalyzed by farnesyltransferase. Accordingly, a farnesyltransferase inhibitor is expected to inhibit the function of the ras oncogene product and thereby to possess antitumor activity.
Known farnesyltransferase inhibitors having a piperazinedione skeleton include gliotoxin and acetylgliotoxin J. Antibiotics, 45, 1802 (1992)!.
Some of the piperazinedione derivatives according to the present invention are known to have activities such as antagonistic activity against platelet activating factors (Japanese Published Unexamined Patent Application No. 233675/86) and antibacterial activity (Ger. Offen. 2029306). However, there has been no report on their farnesyltransferase inhibitory activity or antitumor activity.